This application is based on Japanese Patent Application No. 2001-278329 filed on Sep. 13, 2001, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a cold-accumulating type air conditioner for a vehicle, provided with a cold accumulator (cold storage unit) cooled by cold air after passing through a cooling heat exchanger. This air conditioner is suitably used for a vehicle that temporarily stops a vehicular engine used as a drive source of a compressor, at time of a stoppage of the vehicle or the like.
2. Description of Related Art
In recent years, as an object to protect the environment, a vehicle (economically running vehicle, hybrid vehicle, or the like) automatically stopping an engine thereof at time of a stoppage of the vehicle such as in waiting for a change of a traffic signal has been practically used, and hereafter, there is a tendency to increase the number of vehicles stopping a vehicle engine thereof at the stoppage of the vehicle.
In an air conditioner for a vehicle, a compressor of a refrigerating cycle is generally driven by a vehicular engine. Therefore, in the economically running vehicle or the like described above, at every stoppages of the engine, the compressor is also stopped. Accordingly, a temperature of a cooling heat exchanger (evaporator) is increased, an air temperature blown into a passenger compartment is increased, and therefore, a cooling feeling for a passenger in the passenger compartment is damaged.
To overcome this problem, a cold-accumulating type air conditioner for a vehicle is provided with a cold accumulator. In this air conditioner, the cold accumulator accumulates cold by a cold air after passing through a cooling heat exchanger while a compressor operates, and air blown into the passenger compartment is cooled by the cold accumulator at a stoppage of the compressor. Accordingly, in this case, characteristics of a cold accumulating material sealed in the cold accumulator become very important, for obtaining a suitable cooling function in the cold accumulator.
In view of the above-described problems, it is an object of the present invention to provide a vehicle air conditioner with a cold accumulator having a suitable cold-accumulating cooling function.
It is another object of the present invention to improve cold accumulating performance in the cold accumulator by suitably mixing plural paraffin materials having different melting point.
According to the present invention, in a vehicle air conditioner, a cooling heat exchanger is disposed for cooling air blown into a passenger compartment, and a cold accumulator is disposed at a downstream air side of the cooling heat exchanger to be cooled by cold air after passing through the cooling heat exchanger. The cold accumulator has therein a cold accumulating material that is solidified while being cooled by the cold air from the cooling heat exchanger, and the cold accumulating material is a mixture of plural kinds of materials equal to or more than two, having different melting points. In addition, the plural kinds of materials are mixed so that a melting point of the cold accumulating material is in a range of 7-11xc2x0 C. Generally, the temperature of the cooling heat exchanger is set at about 3xc2x0 C. for restricting front from being caused. Accordingly, the cold accumulating material can be sufficiently solidified by the cold air from the cooling heat exchanger, and air can be sufficiently cooled by latent heat of fusion of the cold accumulating material in the cold accumulator when the cooling heat exchanger is not operated. Thus, by suitably mixing the plural kinds of material to have the melting point in the range of 7-11xc2x0 C., comfortable cooling feeling can be given to a passenger in the passenger compartment by using the latent heat of the fusion of the cold accumulating material in the cold accumulator when the cooling heat exchanger is not operated.
Preferably, the cold accumulating material has an addition agent for improving compatibity between the plural kinds of materials. In this case, a partial solidification or a partial melting is not caused, and cold-accumulating cooling function can be effectively improved in the cold accumulator.
Preferably, all the plural kinds of materials are paraffin-type materials. Specifically, the paraffin-type materials are paraffin C14H30 and paraffin C16H34. Further, the paraffin C14H30 and the paraffin C16H34 are mixed so that a weight ratio of the paraffin C14H30 to the paraffin C16H34 is about ⅓. In this case, the melting point of the cold accumulating material is about 8xc2x0 C., and the cold-accumulating cooling function can be further effectively improved even when the size of the cold accumulator is made smaller.
Further, when the cooling heat exchanger is an evaporator of a refrigerant cycle having a compressor for compressing the refrigerant, while the compressor operates, the operation of the compressor is controlled so that the temperature of an evaporator used as the cooling heat exchanger becomes a target temperature (e.g., 3-5xc2x0 C.). In this case, the melting point of the cold accumulating material is set higher than the target temperature of the evaporator by a predetermined temperature. Accordingly, cold accumulating quantity of the cold accumulating material in the cold accumulator can be effectively increased, and the cooling function can be maintained by the cold accumulating quantity of the cold accumulating material in the cold accumulator when the compressor is stopped.